Resumes suggesting self-centeredness, a need for training or resistance to hard work are correlated with lower employer ratings.

"Know your audience" may well be the central tenet of the art of persuasion. The same principle applies to resumes – in effect, the first step in persuading someone to hire you.

With that in mind, the best place to get resume tips should be your audience: the employer. The problem is that the internet is rife with conflicting advice – just what is the final verdict on including a summary? Furthermore, employers don't always act on their own advice.

Numbers don't lie

ZipRecruiter, a site that allows businesses to post jobs to more than 50 job boards at once, analyzed its database of more than 3 million resumes to determine why some are rated higher than others. On ZipRecruiter, hiring managers rate candidates' resumes on a scale of one to five stars, with one being the worst and five being the best.

"By looking at keywords, length and sections, we were able to create a profile of the perfect cover letter and resume: what you should include, what you shouldn't include, and plenty of tips to help your resume and cover letter stand out from the crowd," Scott Garner, ZipRecruiter's senior corporate communications manager, wrote on the company's blog.

Here's what the data revealed.

Resume tip No. 1: Include a cover letter.

It all starts with the cover letter. ZipRecruiter's research revealed that cover letters increase a resume's chance of receiving a five-star rating by 29%.

"A cover letter is the first chance you have to impress an employer, or to turn them off permanently," Garner wrote.

The study found two keys to a good cover letter: Be polite and display confidence that you'll get the job done. Specifically, the phrase "thank you for your consideration" was included in 10% more of the five-star resumes than those that received just one star.

Resume tip No. 2: Prove your value.

Additionally, since the employer has posted a job because they have a pressing need, job seekers should present themselves as a solution to that problem and not as a work in progress focused only on their own career trajectory.

"Words like 'learning,' 'develop' and 'myself' have a strong correlation with one-star resumes, meaning that employers want a team player who is ready to start contributing to the business on day one," Garner wrote.

A willingness to contribute should not be told but demonstrated with evidence of past performance.

"The biggest mistake folks make on their resume is telling me what their skills are," said Cecilia Deal, a former company recruiter now freelancing as a career coach.

Instead, compelling resumes show, not tell. For example, the phrase "I'm great with people" is not going to convince employers, but "I built my customer base from 100 to 1,000 in 30 days" or "selected as a leader for two key projects" offers proof, Deal said.

Resume tip No. 3: Reorganize your sections.

When formatting a resume, it's critical to only include the sections employers care about. The research revealed that resumes containing "summary," "references," "work history," "objective" and "training" were 1.7 times more likely to earn a five-star rating (that answers that question).

"Employers want to know everything about you that may be relevant to your ability to perform the job they've posted," Garner wrote.

The sections employers find irrelevant were "languages," "personal interests" and "accomplishments." The study discovered that including these sections made it 24% less likely for a resume to receive a top rating.

Resume tip No. 4: Word count matters.

Length also plays a key role in how well hiring managers receive a resume. ZipRecruiter found that managers rated 600- to 700-word resumes much more favorably than resumes with fewer than 500 words. In addition, the more a resume exceeds 700 words, the lower its ratings.

The research also revealed that the summary should be between 90 and 100 words in length and that the objective should be approximately 30 words long.

"Following these length guidelines results in a 30% boost in the chances of receiving a five-star rating," Garner wrote.

Resume tip No. 5: Word choice matters.

When actually writing a resume, job seekers should include certain keywords and avoid others.

The research found that keywords that imply management skills, problem-solving abilities and a proactive stance toward working were associated with the highest ratings. These are some specific "power keywords" that can increase the chances of a five-star rating by up to 70%:

Experience

Management

Project

Development

Business

Skill

Professional

Knowledge

Year

Team

Leadership

Garner cautions job seekers, however, not to go overboard – at a certain point, these keywords have diminishing returns. "Keyword stuffing will more than likely lead to your resume being discarded," Garner wrote. "Make sure you only include words that are relevant to your skills."

ZipRecruiter's analysis also pinpointed words that correlated with low ratings:

Hard

Need

First

Me

Time

Myself

Chance

Develop

Learning

While job seekers shouldn't bend over backward to remove these words from their resume – there's nothing inherently wrong with the words themselves – what they should do is avoid the sentiments these words are often used to convey. That may be the impression that a candidate is self-centered, inexperienced, in need of a great deal of training or put off by hard work.

"Keywords that employers and hiring managers don't want to see are those that are largely overused, often meaningless and don't prove anything unless backed up with solid examples," said Lars Herrem, group executive director at Nigel Wright Group.

For Herrem, phrases like "value-add," "results-driven," "team player," "strategic thinker" and "detail-oriented" should be avoided.

"The takeaway is to replace adjectives with action verbs as much as possible," said Chris Chancey, founder of Amplio Recruiting. This circles back to Tip No. 2 – whereas adjectives simply state your importance, verbs give evidence of your importance.

Experience still matters

While a resume with all the right characteristics correlates with higher ratings, applicants must keep in mind that correlation is not causation.

For example, a resume including the word "management" may be correlated with success, but this doesn't mean finding a way to work "management" into your resume is going to get you an interview. What this probably means is that applicants with managerial experience are more desirable to employers.

In a similar vein, a word count above 500 in and of itself is not going to affect your chances. What's more likely is that, of the 3 million resumes analyzed by ZipRecruiter, poorly rated candidates tended to be those without a lot of experience to report on their resumes, thus lowering their word count.

What job seekers can conclude from these tips is that resumes are more formulaic than we realize. However, nothing replaces actual ability.

Siri Hedreen

Siri Hedreen is a graduate of King’s College London, where she wrote for Roar News, London Student and Edinburgh Festivals Magazine. Find her on Twitter @sirihedreen.